Entrepreneurs and investors are rushing headlong into the nascent legal marijuana industry, fueling a stock craze reminiscent of the late 1990s dot-com bubble and the recent bitcoin mania.

TORONTO—Shannon Soqui just quit his Wall Street job to go after what he thinks is a bigger business: selling marijuana the way Mary Kay Inc. sells cosmetics.

The 51-year-old banker wants to focus on Qind, his San Francisco startup that organizes home parties to sell cannabis products, to get a piece of what he says could sprout into a $100 billion annual business in the U.S.

“It’s like the internet in 1997 or 1998,” said Mr. Soqui. “Investment opportunities to create new businesses have never been more compelling.”